MEMS microactuators located in interior regions of frames having openings therein and methods of operating same

ABSTRACT

A MEMs microactuator can be positioned in an interior region of a frame having at least one opening therein, wherein the frame expands in response to a change in temperature of the frame. A load outside the frame can be coupled to the microactuator through the at least one opening. The microactuator moves relative to the frame in response to the change in temperature to remain substantially stationary relative to the substrate. Other MEMs structures, such as latches that can engage and hold the load in position, can be located outside the frame. Accordingly, in comparison to some conventional structures, temperature compensated microactuators according to the present invention can be made more compact by having the interior region of the frame free of other MEMs structures such as latches.

CLAIM FOR PRIORITY

[0001] The present application is a Continuation-In-Part (CIP) ofdivisional application Ser. No. 09/809,538 filed Mar. 15, 2001, which isa divisional application of parent application Ser. No. 09/261,483,filed Feb. 26, 1999, which issued as U.S. Pat. No. 6,236,139, on May 22,2001. This application claims the benefits of the above-referencedapplications which are hereby incorporated by reference as if set forthherein in their entireties.

FIELD OF THE INVENTION

[0002] The present invention relates to microelectromechanicalstructures, and more particularly to temperature compensated thermallyactuated microelectromechanical structures and associated methods.

BACKGROUND OF THE INVENTION

[0003] Microelectromechanical structures (MEMS) and othermicroengineered devices are presently being developed for a wide varietyof applications in view of the size, cost and reliability advantagesprovided by these devices. Many different varieties of MEMS devices havebeen created, including microgears, micromotors, and other micromachineddevices that are capable of motion or applying force. These MEMS devicescan be employed in a variety of applications including but not limitedto hydraulic applications in which MEMS pumps or valves are utilized andoptical applications which include MEMS light valves and shutters.

[0004] MEMS devices have relied upon various techniques to provide theforce necessary to cause the desired motion within thesemicrostructures. For example, cantilevers have been employed to applymechanical force in order to rotate micromachined springs and gears. Inaddition, some micromotors are driven by electromagnetic fields, whileother micromachined structures are activated by piezoelectric orelectrostatic forces. Recently, MEMS devices that are actuated by thecontrolled thermal expansion of an actuator or other MEMS component havebeen developed. For example, U.S. patent application Ser. Nos.08/767,192; 08/936,598, and 08/965,277 which are assigned to MCNC, theassignee of the present invention, describe various types of thermallyactuated MEMS devices. The contents of each of these applications arehereby incorporated by reference herein. Thermal actuators as describedin these applications comprise arched beams formed from silicon ormetallic materials that further arch or otherwise deflect when heated,thereby creating motive force. These applications also describe varioustypes of direct and indirect heating mechanisms for heating the beams tocause further arching, such that the thermal actuator structures moverelative to other microelectronic structures when thermally actuated.

[0005] In practically every application of MEMS devices, preciselycontrolled and reliable movement is required. Given the micron scaledimensions associated with MEMS structures, stable and predictablemovement characteristics are critically important. The movementcharacteristics of MEMS devices can be affected by intrinsic factors,such as the type of materials used to fabricate the MEMS device, thedimensions and structure of the MEMS device, and the effects ofsemiconductor process variations. All of these intrinsic factors can becontrolled to some extent by the MEMS design engineer. In addition,movement characteristics may be affected by extrinsic factors such asfluctuations in the ambient temperature in which the MEMS deviceoperates, which cannot be controlled by the MEMS design engineer. Whileall of the above factors affect the ability of a MEMS device to moveprecisely and predictably, the impact of these factors may vary fromdevice to device. For instance, while thermally actuated MEMS devicesare affected by all the above factors, they are particularly sensitiveto ambient operating temperature variations because they are thermallydriven devices.

[0006] More particularly, a thermally actuated MEMS device may operateunpredictably or erroneously since the MEMS device will move not only inresponse to thermal actuation caused by active heating or cooling, butalso due to changes in the ambient operating temperature. If ambienttemperatures are very high, parts of a MEMS device designed to move inresponse to thermal actuation may move too much or too far.Alternatively, in very low ambient temperatures, parts of a thermallyactuated MEMS device designed to move may not move sufficiently inresponse to thermal actuation thereof In either temperature extreme,maintaining parts of MEMS device in predictable positions relative toeach other can be difficult. Ambient temperature effects can thus affectthe reliability and limit the possible applications of MEMS thermallyactuated devices. Those skilled in the art will appreciate that similarproblems can arise due to residual stress created by semiconductorprocess variations and structural differences within MEMS devices.

[0007] Therefore, while some thermally activated MEMS structures havebeen developed, it would still be advantageous to develop other types ofthermally actuated structures that would operate more reliably or moreprecisely even when exposed to significant ambient temperaturefluctuations. Consequently, these MEMS structures would be suitable fora wider variety of applications. Numerous applications including but notlimited to switches, relays, variable capacitors, variable resistors,valves, pumps, optical mirror arrays, and electromagnetic attenuatorswould be better served by MEMS structures with these attributes.

SUMMARY OF THE INVENTION

[0008] Pursuant to embodiments according to the present invention, aMEMs device can include first and second spaced apart anchors on asubstrate. A frame is coupled to the first and second anchors. The framedefines an interior region thereof and has at least one opening therein.The frame expands in response to a change in temperature of the frame. Amicroactuator is located in the interior region of the frame and iscoupled to the frame. The microactuator moves relative to the frame inresponse to the change in temperature to remain substantially stationaryrelative to the substrate.

[0009] A load outside the frame can be coupled to the microactuatorthrough the at least one opening. Other MEMs structures, such as latchesthat can engage and hold the load in position, can be located outsidethe frame. Accordingly, in comparison to some conventional structures,temperature compensated microactuators according to the presentinvention can be made more compact by having the interior region of theframe free of other MEMs structures such as latches. For example, insome conventional structures, a microactuator and an associated latchmay both be located in the interior region of a frame.

[0010] In some embodiments according to the present invention, the atleast one opening can be a first opening and a second opening in theframe that are aligned. In some embodiments according to the presentinvention, the microactuator moves parallel to an axis that extendsthrough the at least one opening in response to movement of themicroactuator relative the substrate.

[0011] In some embodiments according to the present invention, the firstand second openings in the frame define first and second opposingportions of the frame that are spaced apart from one another, whereinthe first portion is coupled to the first anchor and the second portionis coupled to the second anchor.

[0012] In some embodiments according to the present invention, the firstanchor is coupled to the first portion of the frame between the firstopening and a temperature compensation portion of the first portion thatmoves in a direction that is substantially orthogonal to movement of themicroactuator in response to the change in temperature. In someembodiments according to the present invention, the first anchor iscoupled to the first portion of the frame at a first position thereof todefine a first temperature compensation portion of the frame to whichthe microactuator is coupled. The second anchor is coupled to the secondportion of the frame at a first position thereof to define a secondtemperature compensation portion of the frame to which the microactuatoris coupled. The first and second temperature compensation portions ofthe frame move in opposite directions in response to the change intemperature. In some embodiments according to the present invention, thefirst and second anchors are between the first and second temperaturecompensation portions of the frame and the first and second openingsrespectively.

[0013] In some embodiments according to the present invention, the firstanchor is coupled to the first portion adjacent to the first opening andthe second anchor is coupled to the second portion adjacent to the firstopening. A third anchor on the substrate is coupled to the first portionand a fourth anchor on the substrate is coupled to the second portion.

[0014] In some embodiments according to the present invention, an RFswitch according to the present invention can include first and secondspaced apart anchors on a substrate. A frame is coupled to the first andsecond anchors. The frame defines an interior region thereof and has atleast one opening therein. The frame expands in response to a change intemperature of the frame. A microactuator is located in the interiorregion of the frame and is coupled to the frame. The microactuator movesrelative to the frame in response to the change in temperature to remainsubstantially stationary relative to the substrate. A member is coupledto the microactuator and extends through the at least one opening in theframe and moves with the microactuator. A latch is on the substrateoutside the interior region of the frame. The latch is engaged with themember in a first latch position to hold the member stationary and isdisengaged from the member in a second latch position to allow themember to move. An RF switch is on the substrate and is coupled to themember. The RF switch is configured to move between an open position anda closed position in response to the movement of the member.

[0015] In some embodiments according to the present invention, a MEMs DCswitch includes first and second spaced apart anchors on a substrate. Aframe is coupled to the first and second anchors. The frame defines aninterior region thereof and has at least one opening therein. The frameexpands in response to a change in temperature of the frame. Amicroactuator is located in the interior region of the frame and iscoupled to the frame. The microactuator moves relative to the frame inresponse to the change in temperature to remain substantially stationaryrelative to the substrate. A member is coupled to the microactuator andextends through the at least one opening in the frame and moves with themicroactuator. A latch is on the substrate outside the interior regionof the frame. The latch is engaged with the member in a first latchposition to hold the member stationary and is disengaged from the memberin a second latch position to allow the member to move. A DC switch ison the substrate and is coupled to the member. The DC switch isconfigured to move between an open position and a closed position inresponse to movement of the member.

[0016] In method embodiments according to the present invention, atemperature compensated latch within a first frame is thermally actuatedto disengaged position that allows a load to move. A temperaturecompensated microactuator within a second frame is thermally actuated tomove the load from a first position to a second position. Thetemperature compensated latch is thermally actuated to an engagedposition to hold the load in the second position.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 provides a schematic plan view of a temperature compensatedMEMS structure according to one embodiment of the present inventionillustrating various positions of the active and temperaturecompensation microactuators.

[0018]FIG. 2 provides a plan view of a temperature compensated MEMSstructure according to one embodiment of the present invention.

[0019]FIG. 3(a) provides a plan view of a temperature compensated MEMSstructure according to another embodiment of the present invention,while

[0020] FIGS. 3(b) and 3(c) provide fragmentary plan views of the maleand female mating surfaces of the temperature compensated MEMS structureof FIG. 3(a) in the closed and open positions, respectively.

[0021]FIG. 4 is a flow chart illustrating the operations performed tooverplate at least a portion of a MEMS structure according to oneembodiment of the present invention.

[0022] FIGS. 5(a) and 5(b) provide plan views of a temperaturecompensated MEMS structure according to another embodiment of thepresent invention at a relative cool temperature and a relatively warmtemperature, respectively, while

[0023]FIG. 5(c) provides a plan view of an temperature compensated MEMSstructure according to another embodiment of the present invention thatincludes direct heating.

[0024]FIG. 6 provides a plan view of another embodiment of a temperaturecompensated MEMS structure according to the present invention thatincludes a frame and an active microactuator.

[0025]FIG. 7 provides a schematic plan view of another embodiment of atemperature compensated MEMS structure according to the presentinvention that provides conductive surfaces and operates as a variablecapacitor.

[0026]FIG. 8 provides a schematic plan view of another embodiment of atemperature compensated MEMS structure according to the presentinvention that provides conductive surfaces and operates as a variableresistor.

[0027]FIG. 9 provides a schematic plan view of another embodiment of atemperature compensated MEMS structure according to the presentinvention that provides valve plates and operates as a valve.

[0028]FIG. 10 provides a schematic plan view of another embodiment of atemperature compensated MEMS structure according to the presentinvention that provides a mirror, attenuator, or the like, moved by anactive microactuator.

[0029]FIG. 11A is a schematic diagram that illustrates embodiments oftemperature compensated microactuators according to the presentinvention.

[0030]FIG. 11B is a perspective view that illustrates embodiments oftemperature compensated microactuators according to the presentinvention.

[0031]FIG. 12 is a schematic diagram that illustrates embodiments oftemperature compensated microactuators according to the presentinvention.

[0032]FIG. 13 is a schematic diagram that illustrates embodiments oftemperature compensated microactuators and associated temperaturecompensated latches according to the present invention.

[0033]FIG. 14 is a block diagram that illustrates embodiments of firstand second opposing latch members, as shown in region A of FIG. 13,according to the present invention.

[0034]FIG. 15 is a schematic diagram that illustrates a load that can becoupled to a temperature compensated microactuator according to thepresent invention.

[0035]FIG. 16 is a schematic diagram that illustrates embodiments of RFswitches according to the present invention.

[0036]FIG. 17 is a schematic diagram that illustrates embodiments of RFswitches according to the present invention.

[0037] FIGS. 18A-D are schematic diagrams that illustrate methodembodiments according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will now be described more fullyhereinafter with reference to the accompanying drawings, in whichpreferred embodiments of the present invention are shown. The presentinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein; rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the present inventionto those skilled in the art. Features in the drawings are notnecessarily to scale, but merely serve to illustrate the presentinvention. Like numbers refer to like elements throughout.

[0039] The present invention provides microelectromechanical structuresand related methods that are adapted to compensate for the effects ofambient temperature changes, residual stress caused by processvariations, and the like in order to provide more predictable andprecise movement. These MEMS structures include an active microactuatoradapted for thermal actuation. When complimentary microactuators areused within the MEMS structure, the active microactuator is adapted tomove in response to the cumulative effect of ambient temperaturevariations and the active alteration of the temperature of the activemicroactuator, such as caused by the active heating of the activemicroactuator. When a frame and active microactuator are used within theMEMS structure, the active microactuator is adapted to move in responseto the active alteration of the temperature of the active microactuator,such as caused by the active heating of the active microactuator.Further, these structures include a temperature compensation element,such as a temperature compensation microactuator or a frame. Althoughnot generally actively heated or cooled, the temperature compensationelement is adapted to move in response to changes in ambient temperaturein order to compensate therefor. According to the present invention, theactive microactuator and the respective temperature compensation elementare adapted to move cooperatively in response to changes in ambienttemperature, such that the active microactuator can be maintained in apredefined spatial or positional relationship over a broad range ofambient temperatures in the absence of active alteration of thetemperature of the active microactuator. As described below, thetemperature compensated MEMS structures can be employed in variousapplications including but not limited to switches, relays, variablecapacitors and resistors, valves, moveable mirror structures, andelectromagnetic attenuators.

[0040] Complimentary Microactuator Structures

[0041] A schematic top view of one embodiment of a temperaturecompensated microelectromechanical structure according to the presentinvention is shown in FIG. 1. The temperature compensatedmicroelectromechanical structure of this embodiment comprises amicroelectronic substrate, an active microactuator, and a temperaturecompensation microactuator. The microelectronic substrate 10 has a firstmajor surface and serves as a base underlying the MEMS temperaturecompensated device. Preferably, the microelectronic substrate comprisesa semiconductor material, such as silicon, although other suitablesubstrate materials may be used. The active microactuator 100 isdisposed on the first major surface of the microelectronic substrate andis adapted to move in response to thermal actuation. In particular, theactive microactuator is adapted to controllably move in response to thecumulative effect of changes in ambient temperature (ΔTA) and activealteration of the temperature (ΔT) of the active microactuator.Typically, the temperature of the active microactuator is activelyaltered by actively heating the active microactuator, although theactive microactuator could also be actively cooled, if so desired. Thetemperature compensation microactuator 200 is also disposed on the firstmajor surface of the microelectronic substrate and is adapted to move inresponse to thermal actuation. While the temperature of the temperaturecompensation microactuator is not generally actively altered, thetemperature compensation microactuator is adapted to controllably movein response to the effect of changes in ambient temperature (ΔTA).

[0042] According to the present invention, the temperature compensatedmicroactuator and the active microactuator are both adapted tocooperatively move in unison or in tandem in response to changes inambient temperature to thereby substantially maintain a predefinedspatial relationship between the temperature compensation microactuatorand the active microactuator over a broad range of ambient temperatures,in the absence of the active alteration of the temperature of themicroactuators. A typical commercial semiconductor device operates inambient temperatures ranging from −40 to 85 degrees Celsius, while atypical mil-spec (military specification) semiconductor device operatesin ambient temperatures ranging from −55 to 125 degrees Celsius.Throughout these broad ranges of ambient temperatures, the temperaturecompensated MEMS structure of the present invention therefore maintainsa predefined spatial relationship between the temperature compensationmicroactuator and the active microactuator in the absence of activealteration of the temperature of the respective microactuators.

[0043] As shown schematically in FIG. 1, for example, the activemicroactuator and the temperature compensation microactuator may beseparated by the same separation distance d1 at both a relatively coolambient temperature as shown in solid lines and at a relatively hotambient temperature as shown in dashed lines since both microactuatorsare adapted to move in unison in response to changes in the ambienttemperature. Upon actively altering the temperature of the activemicroactuator, however, the active microactuator will move differentlythan the temperature compensation microactuator and therefore alter thepredefined spatial relationship therebetween. As shown schematically inFIG. 1, for example, the active microactuator may move to a positionshown in dotted and dashed lines even though the ambient temperatureremains relatively cool so as to reduce the separation distance betweenthe microactuators to d2. As will be hereinafter described, portions ofthe active microactuator and the temperature compensation microactuatorcan eventually be brought into contact with one another followingfurther active alteration of the temperature of the activemicroactuator, such as by further active heating the activemicroactuator, such that the temperature compensation MEMS structure canserve as a relay, a switch or the like. Although not further discussedherein, the temperature compensation microactuator can also be activelyheated or cooled. However, separation distance between themicroactuators will only be altered based upon the temperaturedifferential between the temperature compensation microactuator and theactive microactuator since changes in temperature that affect bothmicroactuators equally will cause both microactuators to move equallysuch that the separation distance remains substantially constant.

[0044] According to the present invention, the active microactuators andthe respective temperature compensation elements, such as the respectivetemperature compensation microactuators, may be disposed in a variety ofpredefined spatial relationships with respect to each other. Forinstance, the active microactuator and temperature compensation elementmay be disposed parallel to, perpendicular to, or in any otherorientation with respect to the first major surface of themicroelectronic substrate. Further, the active microactuator andtemperature compensation element may be disposed within the same plane,in separate planes parallel to the first major surface of the substrate,or in other predefined positional relationships with respect to eachother. However, in one advantageous embodiment that will be furtherdescribed herein below, both the temperature compensation microactuatorand the active microactuator are adapted to move within respectiveplanes that extend generally parallel to the first major surface of themicroelectronic substrate in response to thermal actuation.

[0045] In one embodiment of the present invention, the temperaturecompensation microactuator comprises a first member adapted to move inresponse to changes in ambient temperature. Likewise, the activemicroactuator comprises a second member adapted to move in response tothe cumulative effect of changes in ambient temperature and activealteration of the temperature of the active microactuator. According tothe present invention, the active microactuator and the temperaturecompensation microactuator move in unison in response to changes inambient temperature so as to maintain a predefined spatial relationship,such as a predefined gap for example, between the first and secondmembers in the absence of active alteration of the temperature of theactive microactuator. However, the first member and the second membercan be selectively brought into contact with each other in response tothe active alteration of the temperature of the active microactuator.Thus, these MEMS structures provide members that can controllably andpredictably move in response to thermal actuation over a broad ambienttemperature range.

[0046] One embodiment of a MEMS structure according to the presentinvention having moveable members is illustrated by the example shown inFIG. 2. As described above in conjunction with FIG. 1, the MEMSstructure includes a substrate 10, a temperature compensationmicroactuator 205 and an active microactuator 105. Both the temperaturecompensation microactuator and the active microactuator are mounted uponor affixed to the first major surface of the substrate so as to have apredefined spatial relationship therebetween over a broad range ofambient temperatures in the absence of active alteration of thetemperature of the active microactuator. The active microactuator andtemperature compensation microactuator can comprise any thermally drivenactuator. In addition, while the active microactuator and thetemperature compensation microactuator can be different types ofthermally driven actuators, the active microactuator and the temperaturecompensation microactuator are generally the same type of actuator. Forexample, one or, more preferably, both microactuators can comprisethermal arched beam (TAB) actuators as described in U.S. patentapplication Ser. No. 08/767,192, the contents of which have beenincorporated by reference herein.

[0047] Each thermal arched beam actuator comprises at least two anchorsaffixed to the first major surface of the microelectronic substrate.Each thermal arched beam actuator includes at least one arched beamdisposed between said at least two anchors and spaced from the substratesuch that the arched beam can move relative to the substrate. Forinstance, an active microactuator 105 includes at least one arched beam108 disposed between anchors 106 and 107, while the temperaturecompensation microactuator 205 includes at least arched beam 208disposed between anchors 206 and 207. While the anchors within eachthermal arched beam actuator are affixed to the substrate surface, thearched beams must be released from the microelectronic substrate inorder to move freely and efficiently. Typically, a cavity is formed inthe microelectronic substrate underlying the moving parts within amicroactuator, using established microengineering techniques. A cavityis not required for any active or temperature compensationmicroactuator. However, since a cavity serves to make an activemicroactuator more efficient in operation, a cavity is preferablydisposed underlying the active microactuator. Optionally, a cavity maybe disposed underlying a temperature compensation microactuator. Forinstance, cavity c1 underlies the arched beams 108 and coupler 109disposed between anchors 106 and 107 within active microactuator 105.Also, as shown cavity c2 underlies the arched beams 208 and coupler 209disposed between anchors 206 and 207 within active microactuator 205.

[0048] As described in U.S. patent application Ser. No. 08/936,598, theanchors and the arched beams can be constructed from a conductive metal,such as electroplated nickel. Alternatively, the anchors and the archedbeams may be constructed from a semiconductor material, such as silicon,or any other material having a suitable thermal coefficient of expansionsuch that the arched beams expand or contract in a predictable and anappreciable manner in response to changes in temperature. Typically, anarched beam is formed from a material with a positive coefficient ofthermal expansion that expands with increases in temperature. However,the arched beam can also be formed from a material having a negativecoefficient of thermal expansion that contracts as temperatureincreases.

[0049] Absent active temperature alteration in a quiescent state, eacharched beam has a corresponding position and spatial relationship withrespect to the microelectronic substrate. For the example shown in FIG.2, arched beam 108 within active microactuator 105 will arch apreselected amount and assume a corresponding non-actuated position at agiven quiescent ambient temperature. Consequently, male mating surface213 will have a predefined spatial relationship with respect tocomplimentary female mating surface 212 and to microelectronic substrate10 when arched beam 108 assumes a quiescent position. This occursbecause male mating surface 213 is adapted to move with arched beam 108through coupler 109, and will be positioned accordingly. From aquiescent position, an arched beam within a thermal arched beam actuatoris adapted to move in response to thermal actuation.

[0050] For a thermal arched beam having a positive coefficient ofthermal expansion, increases in the ambient temperature and/or activeheating of the temperature of an arched beam will cause the thermalarched beam to arch further in the same direction in which the archedbeam is already arched, such that the arched beam moves with respect tothe microelectronic substrate. For instance, as shown in FIG. 2, archedbeam 108 within active microactuator 105 will arch further in responseto heating thermal actuation so as to move male mating surface 213closer to the complimentary female mating surface 212. Alternatively,decreases in the ambient temperature and/or active cooling of thetemperature of an arched beam having a positive coefficient of thermalexpansion will reduce the amount that the thermal arched beam is arched.As shown in FIG. 2, arched beam 108 within active microactuator 105 willarch less in response to cooling thermal actuation so as to move malemating surface 213 farther away from the complimentary female matingsurface 212. Once thermal actuation is no longer applied to an archedbeam, the arched beam moves in the opposite sense and reassumes theinitial position and degree of arching associated with the quiescentthermally non-actuated state.

[0051] As described, thermal actuation can be created by ambienttemperature 25 changes or by active alteration of the temperature of amicroactuator. Further, ambient temperatures can increase or decrease inrelation to the ambient temperature corresponding to the quiescentstate. While the temperature of the temperature compensationmicroactuator is not generally actively altered, at least one and, morepreferably, each arched beam of the temperature compensationmicroactuator is adapted to farther arch in response to ambienttemperature increases. In contrast, at least one and, more preferably,each arched beam of the active microactuator is preferably adapted tofurther arch in response to the cumulative effect of increases inambient temperature and the active alteration of the temperature of theactive microactuator. Similarly, generally at least one and, morepreferably, each arched beam of the temperature compensationmicroactuator is adapted to arch to a lesser degree in response toambient temperature decreases. Correspondingly, at least one and, morepreferably, each arched beam of the active microactuator is preferablyadapted to arch to a lesser degree in response to the cumulative effectof decreases in ambient temperature and the active alteration of thetemperature of the active micro actuator.

[0052] Accordingly, the active and temperature compensationmicroactuators are both adapted to respond to changes in ambienttemperature and compensate therefor, thus maintaining the quiescentstate position and spatial relationships. Many techniques may be used toadapt the active and temperature compensation microactuators to move ina predetermined manner in response to changes in ambient temperature.Microactuators can be constructed from materials having differentthermal coefficients of expansion. If thermal arched beam actuatorscomprise the respective microactuators, the length or width of beams candiffer between the active and temperature compensation microactuators.In addition, many techniques may be used to adapt the active andtemperature compensation microactuators to generate a predeterminedamount of force when thermally actuated by active or ambient temperaturevariations. Preferably, the respective microactuators can have adifferent number of similarly constructed arched beams. For instance,the temperature compensated microactuator can have a larger number ofarched beams than the corresponding active microactuator. Differences inthe number of arched beams within a thermal arched beam microactuatorcan be used to control the relative amounts of force generated therein.Those skilled in the art will understand that other techniques notmentioned here may be used to tailor the characteristics of therespective microactuators in response to temperature variations from anysource.

[0053] In order to actively alter the temperature of the activemicroactuator, the active microactuator preferably includes means forheating one or more of the arched beams either directly or indirectly.Although a wide variety of techniques can be utilized to heat the archedbeams as described in U.S. patent application Ser. Nos. 08/767,192 and08/936,598, the means for heating may include means for passingelectrical current through one or more of the arched beams in order todirectly heat the arched beams. For example, a voltage differential canbe applied between the supports such that current flows through thearched beams, thereby heating the arched beams and causing furtherarching. Alternatively, the means for heating can include an externalheater, such as a polysilicon heater that is disposed upon the substrateso as to underlie at least portions of the arched beams. By passingcurrent through the external heater, the external heater will radiateheat that, in turn, will warm the arched beams, thereby indirectlyheating the arched beams and causing further arching. For instance,active microactuator 105 includes heater 440 disposed to heat archedbeam 108, as shown in FIG. 2. Also, heater 442 shown in FIG. 3(a) servesto heat at least one arched beam within active microactuator 110.

[0054] To support an external heater, the substrate generally defines acavity that opens through the first surface and that underlies at leasta portion of the arched beams. As before, the cavity is not required forany microactuator, may be used with any microactuator, and is preferablyincluded in active microactuators. This cavity is preferably formed toincrease the efficiency of arched beams within a thermal arched beamactuator from the underlying microelectronic substrate. For instance,cavity c1 underlying arched beam 108 within active microactuator 105 inFIG. 2, and cavity c3 underlying the arched beams within activemicroactuator 110 in FIG. 3(a) can be constructed in this manner. Whilethe opposed ends of the external heater are disposed upon the firstsurface of the substrate, the medial portions of the external heaterpreferably extend over the cavity so as to be spaced from both thesubstrate and the arched beams. While the external heater can beserpentine in shape as shown in U.S. patent application Ser. Nos.08/767,192 and 08/936,598, the external heater can have a relativelylinear shape as shown in FIG. 2. In this embodiment, the external heater440 extends across the cavity and underlies medial portions of thearched beams in order to heat the beams and to cause further arching. Asshown, the opposed ends of the external heater are disposed on the firstsurface of the substrate on opposite sides of the cavity c1. Inaddition, contact pads 444 and 446 can be defined upon the first surfaceof the substrate in electrical contact with the opposed ends of theexternal heater such that current can directed through the externalheater by applying a voltage differential between the contact pads.

[0055] While the active microactuator has been described hereinabove asincluding means for heating the arched beams, the active microactuatorcould, instead, include other means for actively altering thetemperature of the arched beams. For example, the active microactuatorcan include a cooling device for cooling the arched beams in order toreduce the arching of the beams.

[0056] For the embodiment shown in FIG. 2, each microactuator alsoincludes a member, such as a coupler, that interconnects each thermalarched beam. For example, coupler 109 in the active microactuatorinterconnects three beams, while coupler 209 in the temperaturecompensation microactuator interconnects thirteen beams. Each coupler isadapted to move accordingly in response to thermal actuation of thearched beams connected thereto. Thus, a coupler serves to combine theforces created by the movement of each thermal arched beam in responseto thermal actuation. The couplers of the active and temperaturecompensation microactuators can provide complimentary mating surfaces.For instance, a temperature compensated MEMS structure can have male andfemale mating surfaces with various configurations as shown in FIGS. 2and 3(a). More particularly, the embodiment of FIG. 2 includes an activemicroactuator 105 having a coupler with a male mating surface 213 and atemperature compensation microactuator 205 having a coupler with acomplimentary female mating surface 212.

[0057] According to the present invention, the active microactuator andthe temperature compensation microactuator maintain the same predefinedspatial relationship over a range of ambient temperatures in the absenceof active alteration of the temperature of the microactuators. Thispredefined spatial relationship is perhaps best illustrated by thecorresponding predefined spatial relationship that is maintained betweenthe corresponding mating surfaces. With reference to the embodiment ofFIG. 2, for example, the active microactuator and the temperaturecompensation microactuator maintain a predefined spatial relationship,i.e., a predefined gap, between the corresponding mating surfaces of therespective microactuators over a range of ambient temperatures in theabsence of active alteration of the temperature of the microactuators.

[0058] Once the arched beams of the active microactuator are heated orthe temperature of the arched beams are otherwise actively altered, theactive microactuator will move differently that the temperaturecompensation microactuator such that the microactuators will no longermaintain the predefined spatial relationship, i.e., the predefined gap,between the corresponding mating surfaces. With reference to theembodiment of FIG. 2, for example, actively heating arched beam 108 ofthe active microactuator will move the male mating surface of the activemicroactuator toward the female mating surface of the temperaturecompensation microactuator, thereby decreasing the predefined gapbetween the corresponding mating surfaces of the respectivemicroactuators. With sufficient heating of the arched beams of theactive microactuator, the male mating surface of the activemicroactuator can be moved into contact with the female mating surfaceof the temperature compensation microactuator.

[0059] The microactuators may also include a spring adapted to flex andabsorb mechanical stresses. For instance, mechanical stresses candevelop when the couplers affixed to different microactuators move andselectively contact one another or when a pair of microactuators thatare latched attempt to pull apart, such as upon removal of the activeheating of one of the microactuators. For the example in FIG. 2, thetemperature compensated MEMS structure includes a temperaturecompensation microactuator having a spring 210 that is adapted to flexwhen subjected to forces, such as upon contact of the respectivecouplers. The spring may be formed of various materials having suitablestrength and flexibility such as silicon or a conductive metal. Whilethe spring can have various configurations, the spring of the embodimentshown in FIG. 2 is a generally rectangular loop that is connected to thecoupler proximate the respective mating surface. Alternatively, theembodiment shown in FIG. 3(a) has a generally C-shaped member thatserves a spring function by flexing to permit the rectangular-shapedmember to be inserted into the C-shaped member, moved and supportedtherein, and optionally removed therefrom.

[0060] The temperature compensated MEMS structures of the presentinvention can be employed in a variety of applications. For example, thetemperature compensated MEMS structure can include mating electricalcontacts carried by the temperature compensation microactuator and theactive microactuator in order to form a relay, a switch or the like.Typically, the electrical contacts are fabricated from electroplatednickel that is overplated with a conductive material, as describedbelow, in order to provide high conductivity and reliability whiledelivering excellent resistance to oxidation. In addition, overplatingcan be used to define the minimum interstructure spacing between matingparts. In operation, the male electrical contact and the complimentaryfemale electrical contact can be selectively brought into contact witheach other or, alternatively, separated from one another in response tothe active alteration of the temperature of active microactuatordepending upon whether the contacts are normally open or normallyclosed, respectively, in the absence of the active alteration of thetemperature of the active microactuator.

[0061] One embodiment of a temperature compensated MEMS structure having20 mating male and female contacts is shown in FIG. 2. In thisembodiment, the active microactuator 105 includes a male mating surface213 disposed upon the end of the coupler 109 nearest the temperaturecompensation microactuator. The male mating surface of this embodimentis coated with a conductive material, such as gold, to serve as a maleelectrical contact. Likewise, the temperature compensation microactuatorincludes a complimentary female mating surface 212 disposed upon the endof the coupler 209 nearest the active microactuator. The female matingsurface is also coated with a conductive material, such as gold, toserve as a female electrical contact. In operation, when the activemicroactuator is actively heated, the respective contacts are broughtinto contact and an electrical connection is created therebetween. Inembodiments in which the microactuators are formed of electroplatednickel, the microactuators are also conductive such that the electricalconnection between the contact surfaces also effectively electricallyconnects the microactuators as well as the respective circuits that areconnected to the microactuators as described in U.S. patent applicationSer. Nos. 08/767,192 and 08/936,598. In other embodiments in which themicroactuators are formed of silicon, conductive traces can be formedfrom the electrical contacts to respective contact pads, typicallydisposed upon a respective anchor, which, in turn, may be connected toan electrical circuit. Once the active heating of the activemicroactuator is removed, however, the electrical contacts are againseparated by the predefined gap which is maintained substantiallyconstant over a wide range of ambient temperatures since the activemicroactuator and the temperature compensation microactuator move inunison in response to fluctuations in the ambient temperature.

[0062] An alternative embodiment of a temperature compensated MEMSstructure having male and female electrical contacts is depicted in FIG.3(a). In this embodiment, the temperature compensation microactuator 210comprises a coupler 212 which has a generally C-shaped member 211proximate one end thereof. As shown, the C-shaped member provides afemale mating surface that is coated with a conductive material, such asgold. The active microactuator 110 of this embodiment also comprises acoupler 112 that has a plunger 241 proximate one end thereof. Theplunger provides the male mating surface and is also coated with aconductive material, such as gold.

[0063] In operation, the plunger can be at least partially inserted intothe C-shaped member. In one embodiment, the plunger is in contact withthe edges of the C-shaped member proximate the opening as shown in FIG.3(b) in instances in which the microactuators are subject only toambient conditions and are not actively heated or cooled. Once theactive microactuator is actively heated, however, the plunger is movedinto a center portion of the C-shaped member as shown in FIG. 3(c) so asto no longer contact the C-shaped member. As such, the temperaturecompensated MEMS structure of this embodiment makes contact between therespective conductive mating surfaces in the absence of active heatingof the active microactuator while separating the conductive matingsurfaces in instances in which the active microactuator is activelyheated. Alternatively, the plunger as shown in FIG. 3(c) may beselectively thermally actuated so as to controllably contact theinterior of the C-shaped member, for instance at the solid portionproximate the reference numeral 112 or at the opening of the C-shapedmember. In addition, the plunger shown in FIG. 3(b) may be selectivelythermally actuated so as to controllably contact the exterior of theC-shaped member proximate to the opening. Those skilled in the art willappreciate that many other embodiments are possible wherein the plungerand C-shaped member are adapted to controllably contact each other in avariety of configurations, whether or not the temperature of the activemicroactuator is varied.

[0064] According to either embodiment, the configuration of the matingsurfaces preferably provides for a controlled sliding contact motionbetween the plunger and the C-shaped member. This sliding contactprovides advantages for cleaning impurities that may build up on thecontact surfaces due to the wiping action of the contacts. In thisregard, the application of an overplating of a conductive material, suchas gold, rhodium, or other suitable elements known to form goodelectrical contacts upon nickel mating structures serves to providebetter contact resistance and wear characteristics.

[0065] As previously mentioned, the C-shaped member also functions as aspring 211 by flexing to permit the plunger to be inserted therein. Inaddition, the C-shaped member has a flared opening adapted to guide theplunger into the interior of the C-shaped member. While the plunger andthe C-shaped member are generally designed such that the plunger can beinserted into and removed from the C-shaped member during normaloperation. Optionally, the C-shaped member may be adapted tocontrollably latch the plunger in place inside the C-shaped member.

[0066] As described above, many MEMS structures define a gap in at leastone operative position. In this regard, MEMS relays, switches or thelike, including the embodiments of FIGS. 2 and 3, define a gap between apair of electrical contacts in instances in which the MEMS relay, switchor the like is in an open position. As will be described in more detailhereinbelow, MEMS capacitors can similarly define a separation gapbetween the conductive plates that form the capacitor.

[0067] In order to further improve the performance and reliability ofthese MEMS structures, the size of the gap defined by the MEMSstructures is advantageously defined with even greater levels ofprecision. In this regard, the various gaps defined by conventional MEMSstructures have been typically subject to minimum interstructurespacings in the range of approximately 5 microns or less. While thisrange is suitable for many MEMS applications, evolving MEMS applicationswill demand reduced minimum interstructure spacings and increasedprecision in order to obtain greater performance from the resulting MEMSdevice.

[0068] As such, the present invention also provides an advantageoustechnique for overplating surfaces of a MEMS structure in order to moreprecisely size a gap that is defined by the MEMS structure. As shown inblocks 600 and 610 of FIG. 4, those portions of the MEMS structure thatwill be overplated are photolithographically defined. Typically, a layerof photoresist is deposited over the surface of the MEMS structure and awindow is thereafter opened to expose those portions of the MEMSstructure that define the gap and that are to be overplated. The MEMSstructure is then placed in a plating bath that includes a platingmaterial. See block 620. The plating material is generally a conductivematerial, such as gold, rhodium, silver, rhuthenium, palladium or otherelements known to form good electrical contact, as well as alloysthereof. The plating material is then electroplated onto the exposedportions of the MEMS structure, including those portions of the MEMSstructure that define the gap. See block 630.

[0069] The electroplating process is controlled such that the resultinggap defined by the electroplated portions of the MEMS structure has apredefined size. In this regard, the gap gradually decreases in size asadditional plating material is electroplated onto the exposed portionsof the MEMS structure. By controlling the amount of plating materialthat is electroplated onto the exposed portions of the MEMS structure bycontrolling the rate of deposition and the duration of theelectroplating process, however, the size of the resulting gap definedby the MEMS structure can be precisely defined. In particular, the gapdefined by the overplated portions of a MEMS structure can be preciselydefined to within approximately 0.5 microns. As such, the resulting MEMSstructure should have improved performance characteristics relative toMEMS devices having less well-defined gaps.

[0070] A variety of MEMS structures can be overplated. For example, MEMSstructures having at least two contacts that define a contact separationgap, such as those shown in FIGS. 2 and 3, can be electroplated byoverplating the plating material onto the contacts such that theresulting contact separation gap has a predetermined size. Similarly, aMEMS capacitor, as described hereinbelow, that has at least twoconductive plates and that defines a separation gap can be electroplatedsuch that the plating material is overplated onto the conductive platesin order to create a separation gap having a predefined size. While theoverplating process described above is particularly advantageous forMEMS relays, switches, variable capacitors and the like, the overplatingprocess can also be utilized in conjunction with a wide variety of otherMEMS structures that define gaps that advantageously have a predefinedsize.

[0071] By way of example, the male and female contacts of the MEMS relayof FIG. 3(a) can be overplated, such as with gold, rhodium, silver,rhuthenium, palladium, or other elements known to form good electricalcontacts, as well as alloys thereof, in order to more precisely definethe contact separation gap between the male and female contacts in theopen position. In order to photolithographically define those portionsof the MEMS relays that will be overplated, the surface of the MEMSrelay is initially coated with photoresist. Thereafter, a window isopened that exposes the male and female contacts and that defines theregion to be overplated. For purposes of illustration, FIG. 3(a) depictsthe region 460 to be overplated by speckled shading. The MEMS structureis then placed in a commercially available plating bath, for examplesuch as those that can typically be purchased by those skilled in theart. The exposed portions of the MEMS relay are then electroplated bypassing an appropriate amount of electric current through the platingbath, according to the instructions provided by the manufacturer of theplating bath. Under these conditions, the plating material is typicallydeposited upon the exposed portions of the MEMS relay at a plating rateof approximately 6 microns/hour. Of course, those skilled in the artwill appreciate that many other plating rates may be used while carryingout this aspect of the present invention. The electroplating process canbe temporarily halted prior to completion in order to visually inspectthe MEMS structure and to determine how much more plating materialshould be deposited in order to properly size the gap. Based upon therate at which the plating material is deposited, the MEMS structure canbe reinserted into the plating bath and the electroplating process canbe resumed for a period of time in order to complete the platingprocess. Once a number of MEMS structures have been overplated and theelectroplating process, including the rate at which the plating materialis deposited, has been well characterized, subsequent MEMS structuresmay be overplated by electroplating the MEMS structures for apredetermined period of time without having to temporarily halt theelectroplating process so as to visually inspect the MEMS structure.After removing the current from the plating bath, the overplated MEMSstructure is removed from the plating bath and is washed in water orsome other suitable solvent. The photoresist layer is then removed fromthe remainder of the MEMS structure. As such, the resulting MEMSstructure can define a gap having a size defined to be withinapproximately 0.5 microns. Since the gap can be much more preciselydefined than the gaps of conventional MEMS structures, the overplatedMEMS structures of the present invention correspondingly have improvedperformance characteristics.

[0072] The temperature compensated MEMS structures of the presentinvention can be employed in a wide variety of applications in additionto relays, switches and the like. In particular, the temperaturecompensated MEMS structure can be employed as a variable capacitor. Inthis embodiment of the present invention, the temperature compensationmicroactuator includes a first electrically conductive surface. Avariable capacitor can be constructed from the complimentarymicroactuator structure embodiments or the active microactuator andframe embodiments according to the present invention. For example, asshown in FIG. 7, the temperature compensation microactuator 200 caninclude a first electrically conductive plate 500 that is connected tothe end of the coupler nearest the active microactuator. Likewise, theactive microactuator can include a complimentary second electricallyconductive surface. For example, the active microactuator 100 caninclude a second electrically conductive plate 502 that is connected tothe end of the coupler nearest the temperature compensationmicroactuator.

[0073] The temperature compensated MEMS structure of this embodiment isdesigned such that a predefined spatial relationship is maintainedbetween the respective electrically conductive surfaces over a range ofambient temperatures in the absence of active alteration of thetemperature of the actuators. As such, the first and second electricallyconductive surfaces form a capacitor having a predetermined electricalcapacitance that is substantially maintained constant over the range ofambient temperatures in the absence of active alteration of thetemperature of the microactuators. By actively altering the temperatureof the active microactuator, however, the second electrically conductiveplate can be moved relative to the first electrically conductive platein order to controllably vary the spatial relationship between therespective electrically conductive surfaces and to correspondingly alterthe electrical capacitance established. Since the capacitance can becontrollably varied by selectively moving the active microactuator inresponse to the active alteration of its temperature, the resultingtemperature compensated MEMS structure can serve as a variable capacitorin which the electrical capacitance can be precisely set. The operationof the frame and active microactuator version of the variable capacitoris similar, except that one conductive surface can be disposed eitherinside or outside the frame and active microactuator structure.

[0074] The temperature compensated MEMS structure of another embodimentcan serve as a variable resistor or potentiometer. A variable resistorcan be constructed from the complimentary microactuator structureembodiments or the active microactuator and frame embodiments accordingto the present invention. In this embodiment, the temperaturecompensation microactuator includes a first electrically conductivemember that is typically connected to the end of the coupler nearest theactive microactuator. For example, FIG. 8 shows a first electricallyconductive member 504 connected to temperature compensationmicroactuator 200. The active microactuator 100 also includes a secondelectrically conductive member 506 that is maintained in electricalcontact with the first electrically conductive member. The secondelectrically conductive member of the active microactuator is typicallyconnected to the end of the coupler nearest the temperature compensationmicroactuator. In the absence of the active alteration of thetemperature of the microactuators, the first and second electricallyconductive members cooperate to establish a predetermined resistanceover a wide range of ambient temperatures.

[0075] Upon actively altering the temperature of the activemicroactuator, however, the second electrically conductive member of theactive microactuator is moved relative to the first electricallyconductive member such that the second electrically conductive membercontacts a different portion of the second electrically conductivemember. As a result, the resistance established by the combination ofthe first and second electrically conductive members is correspondinglyaltered. Since the resistance can be controllably varied by selectivelymoving the active microactuator in response to the active alteration ofits temperature, the resulting temperature compensated MEMS structurecan serve as a variable resistor or potentiometer in which theelectrical resistance can be precisely set. The operation of the frameand active microactuator version of the variable resistor is similar,except that either conductive surface can be disposed either inside oroutside the frame and active microactuator structure.

[0076] Other applications of the MEMS temperature compensated structuresdo not require electrically conductive surfaces or members. Inparticular, one embodiment of the present invention provides atemperature compensated MEMS valve. A valve can be constructed from thecomplimentary microactuator structure embodiments or the activemicroactuator and frame embodiments according to the present invention.As in the other applications of the temperature compensated MEMSstructures, temperature compensation is important because the operationof MEMS valves may be adversely impacted in extremely high or extremelylow temperature operating temperatures. One example of a MEMStemperature compensated valve is shown in FIG. 9.

[0077] The temperature compensated MEMS valve of one embodiment includesa temperature compensation microactuator 200 having a first valve plate508 with an opening 509 defined therethrough. The first valve plate andopening can be disposed in numerous orientations and spatialrelationships with respect to the surface of microelectronic substrate10. For example, as shown in FIG. 9, the first valve plate and openingmay be disposed in a plane that intersects the surface of themicroelectronic substrate. Alternatively, the first valve plate andopening may be disposed parallel to the surface of the microelectronicsubstrate, or in some other planar relationship thereto. While the firstvalve plate can be mounted in different manners, the first valve plateis typically attached to the end of the coupler nearest the activemicroactuator. The temperature compensated MEMS valve of this embodimentalso includes a complimentary active microactuator 100 having a secondvalve plate 510, typically attached to the end of the coupler nearestthe temperature compensation microactuator, that is adapted toselectively block at least a portion of the opening defined by the firstvalve plate. For example, in the absence of active alteration of thetemperature of the active microactuator, the second valve plate may bepositioned so as not to cover any portion of the opening defined by thefirst valve plate, notwithstanding wide variations in the ambienttemperature. By actively altering the temperature of the activemicroactuator, however, the second valve plate can be controllablypositioned so as to at least partially block the opening defined by thefirst valve plate.

[0078] As such, the MEMS valve of this embodiment can precisely open,close, or partially open the opening defined by the first valve plate byactively altering the temperature of the active microactuator withoutallowing fluctuations in the ambient operating temperatures to affectthe relative positions of the first and second valve plates. Althoughthe temperature compensated MEMS valve of the illustrated embodiment ispreferably utilized as a light valve, other embodiments of thetemperature compensated MEMS valve can selectively pass fluids, gassesor the like. The operation of the frame and active microactuator versionof the valve is similar, except that either valve plate structure can bedisposed either inside or outside the frame and active microactuatorstructure.

Frame and Microactuator Structures

[0079] Although the temperature compensated MEMS structures describedheretofore have included temperature compensation microactuators, thetemperature compensated MEMS structures of the present invention neednot include temperature compensation microactuators, but can includeother types of temperature compensation elements. As shown in FIGS. 5and 6, for example, a temperature compensated MEMS structure can includea microelectronic substrate, an active microactuator, and a frame actingas a temperature compensation element.

[0080] In this embodiment, the frame and active microactuator overliethe first major surface of microelectronic substrate 10. As before, themicroelectronic substrate preferably comprises a semiconductor material,such as silicon. The frame 420 is disposed upon the first major surfaceand adapted for thermal actuation so as to move in response to changesin ambient temperature (ΔTA). In particular, the frame includes one ormore anchors, such as anchor 421 shown in FIG. 5(a), affixed to thesubstrate with the remainder of the frame being suspended above thesubstrate by the anchors. In addition, the active microactuator 425 isoperably connected to the frame 420 and is adapted to move in responseto the active alteration of the temperature (ΔT) of the activemicroactuator. The frame is adapted to move in response to changes inambient temperature so as to compensate therefor and support the activemicroactuator in substantially the same relative position.

[0081] The thermally compensated MEMS structure of this embodiment isdesigned such that in the absence of active alteration of thetemperature of the active microactuator, the frame and the activemicroactuator cooperatively move in response to changes in ambienttemperature to thereby substantially maintain at least a portion of theactive microactuator in substantially the same relative position withrespect to the microelectronic substrate. Although the thermallycompensated MEMS structure can be designed such that different portionsof the active microactuator are held in position with respect to thesubstrate, the thermally compensated MEMS structure of the illustratedembodiment maintains the leading end of the coupler of the activemicroactuator in a fixed position with respect to the substrate in theabsence of the active alteration of the temperature of the activemicroactuator.

[0082] In the previous embodiment that included both active andtemperature compensation microactuators, the effects of ambienttemperature variations were nullified because the respectivemicroactuators both moved so as to cancel the effects of ambienttemperature. As such, the active and temperature compensationmicroactuators need not be connected to each other. However, in thepresent embodiment that includes a frame and an active microactuator,the effects of ambient temperature variations are canceled because theframe and the active microactuator are operably connected and aredesigned to expand and contract in response to ambient temperaturevariations such that at least a portion of the active microactuatorremains in a fixed position with respect to the substrate. In thisembodiment, the active microactuator 425 has each arched beam disposedwithin the frame and operably connected thereto, rather than anchoreddirectly to the substrate as with the complimentary microactuatorembodiments. As such, the frame can expand or contract in response toambient temperature variations to accommodate the active microactuator,since the frame and active microactuator are adapted to move insubstantially similar proportions. In contrast, when arched beams areaffixed at each end to an anchor, the arched beams move significantlymore than the anchors in response to variations in temperature. However,in the frame and microactuator embodiments, all portions of the activemicroactuator will move relative to both the frame and the underlyingsubstrate in response to the active alteration of the temperature of theactive microactuator.

[0083] Reference is now made to FIGS. 5(a) and 5(b) which illustrate theimpact of changes in ambient temperature, in the absence of any activealteration of the temperature of the active microactuator. In FIG. 5(a),the frame 420 and active microactuator 425 are shown in thermalequilibrium at a first ambient temperature with the leading end of thecoupler 415 being disposed in a particular position d3 with respect tomicroelectronic substrate 10. The arched beams of the activemicroactuator have a given degree of arching or displacement associatedwith the frame ambient temperature, and the frame has a particular sizeand shape to accommodate the active microactuator at this ambienttemperature. Once ambient temperature changes, the frame 400 and theactive microactuator 425 will each change size and shape accordingly.Typically, the frame and active microactuator will expand as temperaturerises, and will contract as the temperature drops.

[0084] As shown in FIG. 5(b), increases in the ambient temperature willcause the 10 arched beams of the active microactuator 425 to expand orarch further. In response to the increased ambient temperatures, frame400 will also expand in each direction. As shown, however, the expansionof the frame, particularly in the width direction, offsets or cancelsthe further arching of the arched beams of the active microactuator suchthat the leading end of the coupler 415 remains in the same relativeposition d3 with respect to the microelectronic substrate 10. Once thetemperature of the active microactuator is actively altered, however,the leading end of the coupler will be moved relative to the substrate.

[0085] The frame and active microactuator embodiments according to thepresent invention can use a variety of heaters and heating techniques,as described previously. Further, one example of direct electricalheating as applied to the frame and active microactuator structureembodiments is shown in FIG. 5(c). The frame 420 is separated at theside proximate to the anchors 421. As such, there is electricalisolation between each portion of the separated frame. Further, theanchors can be used as electrical contacts, each anchor connected to aportion of the separated frame. A source of electrical current may beconnected between the respective anchors in order to drive electricalcurrent through the frame. For example, electrical current is denoted as425 can be introduced through the “+” anchor, as shown. The current isconducted through a first portion of the separated frame 420, through atleast one arched beam, back through the second portion of the separatedframe, and back to the 30 “−” anchor. The cross sectional area of theframe and arched beams can be proportioned so as to create differentelectrical resistances for the frame and arched beams. In this manner,the arched beams can be controllably heated differently, preferablymore, than the separated frame portions. Of course, those skilled in theart understand that this is but one example of the numerous techniquesthat may be used to directly or indirectly heat the frame and activemicroactuator structure.

[0086] Particular embodiments of the temperature compensated MEMSstructure that includes a frame and an active microactuator are depictedin FIGS. 5 and 6. In both embodiments, the frame further comprises atleast one anchor affixed to the first major surface of themicroelectronic substrate such that the remainder of the frame issuspended above the substrate and capable of moving relative to thesubstrate. As shown in FIGS. 5(a) and 5(b), for example, a concave frame420 having a generally C-shape is suspended from a single anchor 421. Assuch, the active microactuator 425 can be disposed within the frame suchthat the leading end of the coupler protrudes through the open end ofthe frame. In an alternative embodiment shown in FIG. 6, the frame 430includes a pair of anchors 431 and 432 for supporting opposite sides ofthe generally closed frame that substantially surrounds the activemicroactuator 435.

[0087] As described above in conjunction with the embodiments of thetemperature compensated MEMS structures that include both active andtemperature compensation microactuators, the temperature compensatedMEMS structures that include a frame and an active microactuator canalso be employed in various applications, at least some of which will bebriefly described herein below. As shown in FIG. 6, the temperaturecompensated MEMS structure of one embodiment includes at least twoelectrical contacts 438 and 440 disposed upon the microelectronicsubstrate 10. The electrical contacts are separated and thereforeinsulated from each other. The active microactuator and, moreparticularly, the leading end of the coupler 436 can include a shortingelectrical contact 441 that can be moved into contact with theelectrical contacts 438 and 440 disposed upon the substrate in responseto active alteration of the temperature of the active microactuator,thereby electrically connecting the electrical contacts disposed uponthe substrate. As a result of the construction of the temperaturecompensated MEMS structure, however, the relative position of theshorting electrical contact with respect to the electrical contactsdisposed upon the substrate will not be effected by changes in theambient temperature since changes in the ambient temperature will notmove the shorting electrical contact relative to the substrate.

[0088] In much the same fashion as described above, the temperaturecompensated MEMS structures that include a frame and an activemicroactuator can also serve as variable capacitor and variable resistorstructures. The illustration used in FIG. 7 also applies herein, exceptwherein active microactuator 100 comprises a frame and activemicroactuator structure for this embodiment, and structures connected tothe temperature compensation microactuator 200 are instead disposed uponthe microelectronic substrate. In order to form a variable capacitor,the temperature compensated MEMS structure includes a first electricallyconductive surface 500 disposed upon the microelectronic substrate. Inaddition, the active microactuator further comprises a complimentarysecond electrically conductive surface 502 that is maintained in apredefined spatial relationship with the first electrically conductivesurface to thereby establish a predetermined electrical capacitancebetween the first and second electrically conductive surfaces over awide range of ambient temperatures in the absence of active alterationof the temperature of the active microactuator. Typically, the secondelectrically conductive surface is provided by an electricallyconductive plate that is operably connected to the coupler, such as theleading end of the coupler. In operation, the capacitance between thefirst and second electrically conductive surfaces can be controllablyvaried by actively altering the temperature of the active microactuatorwhich serves to move the second electrically conductive surface relativeto the first electrically conductive surface.

[0089] Likewise, the temperature compensated MEMS structures thatinclude a frame and an active microactuator can also includeelectrically conductive members that cooperate to form a variableresistor. The illustration used in FIG. 8 also applies herein, exceptwherein active microactuator 100 comprises a frame and activemicroactuator structure for this embodiment, and structure connected tothe temperature compensation microactuator 200 are instead disposed uponthe microelectronic substrate. In this embodiment, a first electricallyconductive member 504 can be disposed upon the microelectronicsubstrate, while the active microactuator includes a complimentarysecond electrically conductive member 506 that electrically contacts aportion of the first electrically conductive member. Although notnecessary for the practice of the present invention, the secondelectrically conductive member commonly extends from the leading end ofthe coupler. As described above, the temperature compensated MEMSstructure is designed such that neither electrically conductive membermoves in response to changes in ambient temperature, thereby maintaininga constant resistance for current traveling through the conductivemembers. However, the second electrically conductive member will bemoved in response to active alteration of the temperature of the activemicroactuator such that the resistance for current traveling through theconductive members is correspondingly changed. By actively altering thetemperature of the active microactuator in a controlled fashion in orderto selectively position the second electrically conductive memberrelative to the first electrically conductive member, the temperaturecompensated MEMS structure functions as a variable resistor.

[0090] The temperature compensated MEMS structure can also provide avalve to selectively pass light, fluid, gasses or the like. Theillustration used in FIG. 9 also applies herein, except wherein activemicroactuator 100 comprises a frame and active microactuator structurefor this embodiment, and structures connected to the temperaturecompensation microactuator 200 are instead disposed upon themicroelectronic substrate. For purposes of illustration, however, atemperature compensated MEMS structure that provides a light valve willbe hereinafter described. In this embodiment, the temperaturecompensated MEMS structure includes a first valve plate 508 disposedupon the substrate. The first valve plate defines a passage 509therethrough. The active microactuator also includes a second valveplate 510, such as a solid valve plate, that can cooperate with thefirst valve plate to selectively block at least a portion of the passagein response to active alteration of the temperature of the activemicroactuator. The first valve plate and passage can be disposed innumerous orientations and spatial relationships with respect to thesurface of microelectronic substrate 10. For example, as shown in FIG.9, the first valve plate and opening may be disposed in a plane thatintersects the surface of the microelectronic substrate. Alternatively,the first valve plate and opening may be disposed parallel to thesurface of the microelectronic substrate, or in some other planarrelationship thereto. Since the second valve plate is attached to thatportion of the active microactuator that remains in a fixed positionwith respect to the substrate as the ambient temperature changes, thevalve is immune to fluctuations in the ambient temperature since neithervalve plate will change its relative position. Another embodiment of atemperature compensated MEMS device of the present invention furtherincludes a mirror, an attenuator of electromagnetic radiation or thelike (hereinafter collectively referenced as a mirror) that is adaptedfor movement with the active microactuator. The mirror, attenuator, andthe like may be disposed upon the active microactuator of either thecomplimentary microactuator or frame and active microactuatorstructures. Preferably, the mirror is disposed upon an activemicroactuator within a frame. In particular, for the example shown inFIG. 10, the mirror 520 is mounted upon that portion of the activemicroactuator 525 that remains in a fixed position with respect to thesubstrate as the ambient temperature changes such that the relativeposition of the mirror with respect to the microelectronic substrate issubstantially maintained constant over a broad range of ambienttemperatures in the absence of active alteration of the temperature ofthe microactuator. However, the relative position of the mirror isselectively modified by actively altering the temperature of the activemicroactuator. As such, the mirror can be controllably moved into or outof a beam of light by actively altering the temperature of the activemicroactuator while preventing changes in the ambient temperature fromaltering the relative position of the mirror.

[0091] As described above, the various embodiments of MEMS temperaturecompensated structures can therefore be utilized in a wide variety ofapplications, such as switches, relays, variable capacitors, variableresistors, valves, moveable mirror structures, and electromagneticattenuators. Those skilled in the art will understand that otherapplications not mentioned herein may exist for the present invention.As such, the temperature compensated MEMS structures of the presentinvention can be employed in various applications that demand or prefermoveable structures wherein components are adapted to move in a preciseand predictable manner without being adversely effected by variations inambient temperature or fabrication processes.

[0092] Pursuant to further embodiments according to the presentinvention, a MEMs microactuator can be positioned in an interior regionof a frame having at least one opening therein. A load outside the framecan be coupled to the microactuator through the at least one opening.Other MEMs structures, such as latches that can engage and hold the loadin position, can be located outside the frame. Accordingly, incomparison to some conventional structures, temperature compensatedmicroactuators according to the present invention can be made morecompact by having the interior region of the frame free of other MEMsstructures such as latches. For example, in some conventionalstructures, a microactuator and an associated latch may both be locatedin the interior region of a frame.

[0093]FIG. 11A is a schematic diagram that illustrates embodiments oftemperature compensated microactuators 1100 according to the presentinvention. FIG. 11B is a perspective view that illustrates embodimentsof temperature compensated microactuators 1100 according to the presentinvention.

[0094] A microactuator 1130 on a substrate 1101 is located in aninterior region 1115 of a frame. The microactuator 1130 is coupled tothe frame by thermal actuated beams (TABs) 1135. The frame can includetwo opposing portions 1110 a-b which are attached to the substrate 1101by anchors 1105 a-d. The two opposing portions 1110 a-b define first andsecond openings 1120 a-b.

[0095] More or fewer anchors may be used. For example, in someembodiments according to the present invention as illustrated in FIG.11A, the second and fourth anchors 1105 b, 1105 d may be eliminated.

[0096] The first portion of the frame 1110 a is connected to thesubstrate 1101 by the first and second anchors 1105 a-b. The secondportion of the frame 1110 b is attached to the substrate 1101 by thesecond and third anchors 1105 c-d. The first portion of the frame 1110 ais released from the substrate 1101 between the first and second anchors1105 a-b. The second portion of the frame 1110 b is also released fromthe substrate 1101 between third and fourth anchors 1105 c-d. Themicroactuator 1130 can include a heater 1142 on the microactuator 1130.In some embodiments according to the present invention, current ispassed through the heater 1142 via electrical contacts 1141 a-b. Theheater 1142 can cause the TABs 1135 to expand thereby causing themicroactuator 1130 to move in a direction 1140 that is parallel to anaxis 1121 that extends through at least one of the openings 1120 a-b inthe frame.

[0097] Although FIG. 11A shows a frame having two opposing portions, insome embodiments according to the present invention a single opposingportion of the frame may be used. For example, in some embodimentsaccording to the present invention, the microactuator can be coupled tothe first portion of the frame 1110 a. In such embodiments according tothe present invention, the microactuator may be in contact with a railor other structure adjacent to the microactuator and opposite the firstportion of the frame 1110 a so that expansion of the TABs 1135 can causethe microactuator to move in the direction 1140 when the TABs 1135 areheated.

[0098] Changes in the temperature of the frame 1110 can be compensatedfor by the expansion of the first and second opposing portions of theframe 1110 a-b in opposite directions 1125 a-b. As the ambienttemperature surrounding the first portion of the frame 1110 a changes,the first portion of the frame 1110 a can expand in the direction 1125a. The second portion of the frame 1110 b can also expand in thedirection 1125 b which is opposite to the direction 1125 a. As the firstand second opposing portions of the frame 1110 a-b move in the opposingdirections 1125 a-b, movement of the microactuator 1130 due to expansionof the TABs 1135 as a result of the changes in ambient temperature canbe compensated for thereby allowing the microactuator 1130 to remainsubstantially stationary relative to the substrate 1101. The first andsecond portions of the frame 1110 a,b and the thermal arched beams 1135can be made of the same material so that the respective expansion ofeach due to changes in ambient temperature effectively offset oneanother. In some embodiments, the first and second portions of the frame1110 a,b and the thermal arched beams 1135 are made of nickel. Othermaterials can be used.

[0099] Allowing the microactuator to remain substantially stationaryrelative to the substrate may enable more accurate actuation of themicroactuator over a wide range of ambient temperatures. For example,according the present invention, a substantially equal currents may beused to thermally actuate the microactuator a distance relative to thesubstrate at tow different ambient temperatures thereby enabling moreaccurate control of the movement of the microactuator over a range ofambient temperatures.

[0100] Although FIG. 11A shows that the first and second openings 1120a-b are aligned with one another in one way, it will be understood thatthe first and second openings may be aligned in other ways or unalignedwith one another. The size of the openings may also be different thanone another. In some embodiments according to the present invention, theframe may include only one opening therein.

[0101]FIG. 12 is a schematic diagram that illustrates embodiments oftemperature compensated microactuators 1200 according to the presentinvention. A microactuator 1230 is located in an interior region 1215 ofa frame having two openings 1220 a-b therein. The frame includes firstand second opposing portions 1210 a-b. The microactuator 1230 is coupledto the first and second opposing portions of the frame 1210 a-b by TABs1235.

[0102] The first portion of the frame 1210 a is attached to thesubstrate 1201 by first and second anchors 1205 a-b. A temperaturecompensation portion 1250 a of the first portion of the frame 1210 a isreleased from a substrate 1201 between the first and second anchors 1205a-b. A second temperature compensation portion 1250 b of the secondportion of the frame 1210 b is released from the substrate 1201 betweenthe third and fourth anchors 1205 c-d. As the ambient temperaturesurrounding the first and second portions 1210 a-b of the frame changes,the respective opposing portions of the frame 1210 a-b can expand infirst and second opposing directions 1225 a-b to keep the microactuator1230 substantially stationary relative to the substrate 1201 as theambient temperature changes.

[0103] The amount of expansion in the first and second opposingdirections 1225 a-b as a result of a change in ambient temperature canbe controlled by a distance between the anchors 1205 a-b, 1205 c-d andend points 1206 a-b of the temperature compensation portions 1250 a-brespectively. For example, more temperature compensation can be providedby spacing the anchors 1205 a-b, 1205 c-d farther apart from the endpoints 1206 a-b of the temperature compensation portions 1250 a-b.Conversely, less temperature compensation can be provided by spacing theanchors 1205 a-b, 1205 c-d closer to the end points 1206 a-b of thetemperature compensation portions 1250 a-b. In particular, the firsttemperature compensation portion 1250 a can provide an amount oftemperature compensation based on the spacing between the first andsecond anchors 1205 a,b and the end-point of the first temperaturecompensation portion 1250 a. Similarly, the second portion of the frame1210 b can provide temperature compensation based on the spacing betweenthird and fourth anchors 1205 c-d and the end-point of the secondtemperature compensation portion 1250 b.

[0104] The portions of the frame 1210 located between the anchors andthe first and second openings 1220 a-b may or may not be released fromthe substrate 1201. It will be understood that although FIGS. 11 and 12show that the first and second portions of the frame are mirror imagesof one another, in some embodiments according to the present invention,the first and second opposing portions of the frame are not mirrorimages of one another. Furthermore, other shapes may be used to providethe first and second opposing portions of the frame.

[0105]FIG. 13 is a schematic diagram that illustrates embodiments oftemperature compensated microactuators 1300 a and associated temperaturecompensated latches 1300 b-c according to the present invention. Thetemperature compensated microactuator 1300 a according to the presentinvention can be coupled to a load 1370 by member 1360 a that extendsthrough an opening in the frame associated with the temperaturecompensated microactuator 1300 a. The first and second temperaturecompensated latch microactuators 1300 b-c according to the presentinvention can be located adjacent to the temperature compensatedmicroactuator 1300 a on the same substrate. The first and secondtemperature compensated latch microactuators 1300 b-c are coupled tofirst and second latch members 1360 b-c through openings in therespective associated frames. According to the present invention, thetemperature compensated microactuator 1300 a and the first and secondtemperature compensated latch microactuators 1300 b-c can each betemperature compensated by respective frames associated therewith toallow the size of the entire MEMs structure to be reduced in comparisonto some conventional structures.

[0106] Although FIG. 13 shows two opposing temperature compensated latchmicroactuators 1300 b-c, it will be understood that a single temperaturecompensated latch microactuator may be used. It will also be understoodthat the latches 1300 b-c may not be temperature compensated.

[0107] In operation, the temperature compensated microactuator 1300 acan be thermally actuated to move the load 1370 between first and secondload positions such as opened and closed positions associated with aswitch. The first and second temperature compensated latchmicroactuators 1300 b-c can engage the member 1360 a, as shown in regionA of FIG. 13, to maintain a position of the load 1370 without requiringactive actuation of the temperature compensation microactuator 1300 a.For example, once the load 1370 is moved to a first position by thetemperature compensated microactuator 1300 a, the first and secondtemperature compensated latch microactuators 1300 b-c can engage themember 1360 a to hold the load 1370 in position. The thermal actuationof the temperature compensated microactuator 1300 a may then be ceasedor reduced while the first and second temperature compensated latchmicroactuators 1300 b-c hold the load in position.

[0108]FIG. 14 is a block diagram that illustrates first and secondopposing latch members 1460 b-c, as shown in region A of FIG. 13, thatare configured to engage or disengage a member 1460 to hold the member1460 in position or allow the member 1460 to move. The latch members1460 b-c can have teeth which can engage the member 1460. The surface ofthe member 1460 opposite the first latch member 1460 b can be contouredin a complementary pattern to that on the first latch member 1460 b.Similarly, the surface on the opposing side of the member 1460 can becontoured in a complementary pattern to that on the second latch member1460 c. Although the first and second latch members 1460 b-c are shownhaving the same contours, it will be understood that different contourscan be used for each of the latch members. Although the first and secondlatch members 1460 b-c and the member 1460 are shown as havingteeth-contoured surfaces, it will also be understood that other types ofcontours can be used in other embodiments according to the presentinvention.

[0109]FIG. 15 is a schematic diagram that illustrates a load 1570 thatcan be coupled to a temperature compensated microactuator according tothe present invention, as shown for example, in FIG. 13. In particular,the load 1570 can be a dual contact DC switch that provides a DC signalat a first terminal 1572. The first terminal 1572 can be moved betweenan open position and a closed position. In the open position the firstterminal 1572 is separated from a pair of second terminals 1574 a-b. Thetemperature compensated microactuator according to the present inventioncan move the first terminal 1572 to the closed position to be inelectrical contact with at least one of the second terminals 1574 a-b. ADC signal can flow from the first terminal 1572 to at least one of thesecond terminals 1574 a-b when the DC switch is in the closed position.

[0110]FIG. 16 is a block diagram that illustrates embodiments of RFswitches according to the present invention. The RF switch can move aload 1665 between first and second positions, such as opened and closedpositions. As shown in FIG. 17, the load 1665 includes a first terminal1772 which can provide an RF signal and a second terminal 1775 that iscoupled to the temperature compensated microactuator according to thepresent invention. In the opened position, the first terminal 1772 isspaced apart from the second terminal 1775 so that the RF signal is notconducted from the first terminal 1772 to the second terminal 1775. Thetemperature compensated microactuator can move the second terminal 1775to the closed position to electrically contact the first terminal 1772.In the closed position, the RF signal can be conducted from the firstterminal 1772 to the second terminal 1775 onto an RF signal path 1780.The RF signal path 1780 can be shielded from noise by an RF ground 1785.

[0111] FIGS. 18A-D are schematic diagrams that illustrate methodembodiments according to the present invention. In particular, each ofthe figures shows three microactuators including a region A where latchmembers 1890 a-b can engage a member 1885. An enlarged view of theregion A is shown for each state associated with the microactuators.

[0112] In FIG. 18A, first and second temperature compensated latchmicroactuators 1800 b-c are thermally actuated to disengage from themember 1885. In FIG. 18B, the temperature compensated microactuator 1800a is thermally actuated to move the member 1885, and the load attachedthereto, to a first position. In FIG. 18C, the thermal actuation of thetemperature compensated latch microactuators 1800 b-c is ceased orreduced to engage the first and second latch members 1890 a-b with themember 1885 to thereby hold the member 1885 and the load in position. InFIG. 18D, thermal actuation of all of the temperature compensatedmicroactuators 1800 a-c is ceased or reduced while the load ismaintained in position by the latch members 1890 a-b being engaged withthe member 1885.

[0113] In embodiments according to the present invention, a MEMsmicroactuator can be positioned in an interior region of a frame havingat least one opening therein. A load outside the frame can be coupled tothe microactuator through the at least one opening. Other MEMsstructures, such as latches that can engage and hold the load inposition, can be located outside the frame. Accordingly, in comparisonto some conventional structures, temperature compensated microactuatorsaccording to the present invention can be made more compact by havingthe interior region of the frame free of other MEMs structures such aslatches.

[0114] In the drawings and specification, there have been disclosedtypical preferred embodiments of the present invention and, althoughspecific terms are employed, they are used only in a generic anddescriptive sense only and not for purposes of limiting in any respectthe scope of the present invention as set forth in the following claims.

What is claimed:
 1. A MEMs device comprising: a substrate; a firstanchor on the substrate; a second anchor on the substrate and spacedapart from the first anchor; a frame coupled to the first and secondanchors, that defines an interior region thereof and having at least oneopening therein, wherein the frame expands in response to a change intemperature of the frame; and a microactuator in the interior region ofthe frame and coupled to the frame, wherein the microactuator movesrelative to the frame in response to the change in temperature to remainsubstantially stationary relative to the substrate.
 2. A MEMs deviceaccording to claim 1 wherein the at least one opening comprises a firstopening and a second opening in the frame that is aligned with the firstopening.
 3. A MEMs device according to claim 1 wherein the microactuatormoves parallel to an axis that extends through the at least one openingin response to movement of the microactuator relative the substrate. 4.A MEMs device according to claim 2 wherein the first and second openingsin the frame define first and second opposing portions of the frame thatare spaced apart from one another; wherein the first portion is coupledto the first anchor; and wherein the second portion is coupled to thesecond anchor.
 5. A MEMs device according to claim 4 wherein the firstanchor is coupled to the first portion of the frame between the firstopening and a temperature compensation portion of the first portion thatmoves in a direction that is substantially orthogonal to movement of themicroactuator in response to the change in temperature.
 6. A MEMs deviceaccording to claim 4: wherein the first anchor is coupled to the firstportion of the frame at a first position thereof to define a firsttemperature compensation portion of the frame to which the microactuatoris coupled; wherein the second anchor is coupled to the second portionof the frame at a first position thereof to define a second temperaturecompensation portion of the frame to which the microactuator is coupled;and wherein the first and second temperature compensation portions ofthe frame move in opposite directions in response to the change intemperature.
 7. A MEMs device according to claim 6 wherein the first andsecond anchors are between the first and second temperature compensationportions of the frame and the first and second openings respectively. 8.A MEMs device according to claim 4 wherein the first anchor is coupledto the first portion adjacent to the first opening and the second anchoris coupled to the second portion adjacent to the first opening, the MEMsdevice further comprising: a third anchor on the substrate coupled tothe first portion; and a fourth anchor on the substrate coupled to thesecond portion.
 9. A MEMs device according to claim 8: wherein the firstanchor is coupled to the first portion of the frame at a first positionthereof; wherein the second anchor is coupled to the second portion ofthe frame at a first position thereof relative to the first opening;wherein the third anchor is coupled to the first portion of the frame ata second position thereof to define a first temperature compensationportion of the frame between the first and second positions of the firstportion to which the microactuator is coupled; wherein the fourth anchoris coupled to the second portion of the frame at a second positionthereof to define a second temperature compensation portion between thefirst and second positions of the second portion to which themicroactuator is coupled; and wherein the first and second temperaturecompensation portions of the frame move in opposite directions inresponse to the change in temperature.
 10. A MEMs device according toclaim 1 further comprising: a latch on the substrate outside theinterior region of the frame that is coupled to the microactuator by amember that extends through the at least one opening.
 11. A MEMs deviceaccording to claim 10 wherein the latch holds the member in positionwhen engaged therewith.
 12. A MEMs device according to claim 10 whereinthe latch comprises first and second latch portions that engage themember from opposite sides of the member.
 13. A MEMs device according toclaim 1: wherein the microactuator is coupled to a load that is outsidethe interior region of the frame.
 14. A MEMs device according to claim 1wherein the frame extends in at least two directions to define theinterior portion.
 15. A MEMs Radiofrequency (RF) switch comprising: asubstrate; a first anchor on the substrate; a second anchor on thesubstrate and spaced apart from the first anchor; a frame, coupled tothe first and second anchors, that defines an interior region thereofand having at least one opening therein, wherein the frame expands inresponse to a change in temperature of the frame; a microactuator in theinterior region of the frame and coupled to the frame, wherein themicroactuator moves relative to the frame in response to the change intemperature to remain substantially stationary relative to thesubstrate; a member, coupled to the microactuator, that extends throughthe at least one opening in the frame and moves with the microactuator;a latch on the substrate outside the interior region of the frame thatis engaged with the member in a first latch position to hold the memberstationary and is disengaged from the member in a second latch positionto allow the member to move; and an RF switch, on the substrate andcoupled to the member, that is configured to move between an openposition and a closed position in response to the movement of themember.
 16. A MEMs RF switch according to claim 15, wherein the latchfurther comprises: a temperature compensated latch microactuator on thesubstrate, configured to move the latch between the first and secondlatch positions in response to thermal actuation of the temperaturecompensated latch microactuator to engage the member, the temperaturecompensated latch microactuator further comprising: a first latch anchoron the substrate; a second latch anchor on the substrate and spacedapart from the first latch anchor; a latch frame coupled to the firstand second latch anchors, that defines an interior region thereof andhaving at least one opening therein, wherein the latch frame expands inresponse to a change in temperature of the latch frame; and a latchmicroactuator in the interior region of the latch frame and coupled tothe latch frame, wherein the latch microactuator moves relative to thelatch frame in response to the change in temperature to remainsubstantially stationary relative to the substrate.
 17. A MEMs RF switchaccording to claim 16 wherein the temperature compensated latchmicroactuator comprises a first temperature compensated latchmicroactuator, the RF switch further comprising: a second temperaturecompensated latch microactuator, on the substrate adjacent the memberand opposite the first temperature compensated latch microactuator,configured to engage the member.
 18. A MEMs RF switch according to claim15 wherein the RF switch further comprises: a first RF terminalconfigured to provide an RF signal; a second RF terminal coupled to theRF switch that is electrically coupled to the first RF terminalconfigured to conduct the RF signal from the first to the second RFterminal when the RF switch is in the closed position; and an RF shieldadjacent to the second RF terminal and the RF switch that protects theRF signal from noise.
 19. A MEMs DC switch comprising: a substrate; afirst anchor on the substrate; a second anchor on the substrate andspaced apart from the first anchor; a frame, coupled to the first andsecond anchors, that defines an interior region thereof and having atleast one opening therein, wherein the frame expands in response to achange in temperature of the frame; a microactuator in the interiorregion of the frame and coupled to the frame, wherein the microactuatormoves relative to the frame in response to the change in temperature toremain substantially stationary relative to the substrate; a member,coupled to the microactuator, that extends through the at least oneopening in the frame and moves with the microactuator; a latch on thesubstrate outside the interior region of the frame that is engaged withthe member in a first latch position to hold the member stationary andis disengaged from the member in a second latch position to allow themember to move; and a DC switch, on the substrate and coupled to themember, that is configured to move between an open position and a closedposition in response to movement of the member.
 20. A MEMs DC switchaccording to claim 19, wherein the latch further comprises: atemperature compensated latch microactuator on the substrate, configuredto move the latch between the first and second latch positions inresponse to thermal actuation of the temperature compensated latchmicroactuator to engage the member, the temperature compensated latchmicroactuator further comprising: a first latch anchor on the substrate;a second latch anchor on the substrate and spaced apart from the firstlatch anchor; a latch frame coupled to the first and second latchanchors, that defines an interior region thereof and having at least oneopening therein, wherein the latch frame expands in response to a changein temperature of the latch frame; and a latch microactuator in theinterior region of the latch frame and coupled to the latch frame,wherein the latch microactuator moves relative to the latch frame inresponse to the change in temperature to remain substantially stationaryrelative to the substrate.
 21. A MEMs DC switch according to claim 20,wherein the temperature compensated latch microactuator comprises afirst temperature compensated latch microactuator, the DC switch furthercomprising: a second temperature compensated latch microactuator, on thesubstrate opposite the first temperature compensateds latchmicroactuator, configured to enage the member.
 22. A MEMs DC switchaccording to claim 15, wherein the DC switch further comprises: a firstDC terminal configured to provide a DC signal; a second DC terminalconfigured to provide the DC signal, wherein at least one of the firstand second DC terminals is electrically coupled to the DC switch whenthe DC switch is in the closed position.
 23. A method of operating aMEMs device comprising: thermally actuating a temperature compensatedlatch within a first frame to a disengaged position that allows a loadto move; thermally actuating a temperature compensated microactuatorwithin a second frame to move the load from a first position to a secondposition; and thermally actuating the temperature compensated latch toan engaged position to hold the load in the second position.
 24. Amethod according to claim 23 wherein the thermally actuating thetemperature compensated latch to an engaged position comprises reducingheat applied to the temperature compensated latch.
 25. A methodaccording to claim 23 further comprising: reducing heat applied to thetemperature compensated microactuator; and reducing heat applied to thetemperature compensated latch.